The Experts below are selected from a list of 240 Experts worldwide ranked by ideXlab platform
Lena H Ting - One of the best experts on this subject based on the ideXlab platform.
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lower limb rigidity is associated with frequent falls in parkinson s disease
Movement Disorders Clinical Practice, 2019Co-Authors: Lucas J Mckay, Madeleine E Hackney, Stewart A Factor, Lena H TingAbstract:Background and Objective The role of muscle rigidity as an etiological factor of falls in Parkinson's disease (PD) is poorly understood. Our objective was to determine whether lower leg rigidity was differentially associated with frequent falls in PD compared to upper limb, neck, and total rigidity measures. Methods We examined the associations between Unified Parkinson's Disease Rating Scale-Part III (motor) rigidity subscores and the history of monthly or more frequent falls in 216 individuals with PD (age, 66 ± 10 years; 36% female; disease duration, 7 ± 5 years) with logistic regression. Results A total of 35 individuals were frequent fallers. Significant associations were identified between lower limb rigidity and frequent falls (P = 0.01) after controlling for age, sex, PD duration, total Unified Parkinson's Disease Rating Scale- Part III score, and presence of freezing of gait. No significant associations (P ≥ 0.14) were identified for total, arm, or neck rigidity. Conclusion Lower limb rigidity is related to frequent falls in people with PD. Further investigation may be warranted into how parkinsonian rigidity could cause falls.
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lower limb rigidity is associated with frequent falls in parkinson disease
bioRxiv, 2019Co-Authors: Lucas J Mckay, Madeleine E Hackney, Stewart A Factor, Lena H TingAbstract:Abstract BACKGROUND AND OBJECTIVE: The role of muscle rigidity as an etiological factor of falls in Parkinson disease (PD) is poorly understood. Our objective was to determine whether lower leg rigidity was differentially associated with frequent falls in PD compared to upper limb, neck, and total rigidity measures. METHODS: We examined associations between UPDRS-III (motor) rigidity subscores and history of monthly or more frequent falls in N=216 individuals with PD (age, 66±10 y; 36% female, disease duration, 7±5 y) with logistic regression. RESULTS: N=35 individuals were frequent fallers. Significant associations were identified between lower limb rigidity and frequent falls (P=0.01) after controlling for age, sex, PD duration, total UPDRS-III score, and presence of FOG. No significant associations (P≥0.14) were identified for total, arm, or neck rigidity. CONCLUSION: Lower limb rigidity is related to frequent falls in people with PD. Further investigation may be warranted into how parkinsonian rigidity could cause falls. Financial Disclosures/Conflict of Interest concerning the research related to the manuscript: None Funding: NIH K25HD086276, R01HD046922, R21HD075612, UL1TR002378, UL1TR000454; Department of Veterans Affairs R&D Service Career Development Awards E7108M and N0870W, Consolidated Anti-Aging Foundation, and the Sartain Lanier Family Foundation.
A. J. Rader - One of the best experts on this subject based on the ideXlab platform.
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thermostability in rubredoxin and its relationship to mechanical rigidity
Physical Biology, 2009Co-Authors: A. J. RaderAbstract:The source of increased stability in proteins from organisms that thrive in extreme thermal environments is not well understood. Previous experimental and theoretical studies have suggested many different features possibly responsible for such thermostability. Many of these thermostabilizing mechanisms can be accounted for in terms of structural rigidity. Thus a plausible hypothesis accounting for this remarkable stability in thermophilic enzymes states that these enzymes have enhanced conformational rigidity at temperatures below their native, functioning temperature. Experimental evidence exists to both support and contradict this supposition. We computationally investigate the relationship between thermostability and rigidity using rubredoxin as a case study. The mechanical rigidity is calculated using atomic models of homologous rubredoxin structures from the hyperthermophile Pyrococcus furiosus and mesophile Clostridium pasteurianum using the FIRST software. A global increase in structural rigidity (equivalently a decrease in flexibility) corresponds to an increase in thermostability. Locally, rigidity differences (between mesophilic and thermophilic structures) agree with differences in protection factors.
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Thermostabilization Due to Rigidity: A Case Study of Rubredoxin
Biophysical Journal, 2009Co-Authors: A. J. RaderAbstract:The source of increased stability in proteins from organisms that thrive in extreme thermal environments is not well understood. Previous experimental and theoretical studies have suggested many different features responsible for such thermostability. Many of these thermostabilizing mechanisms can be accounted for in terms of structural rigidity. Thus a plausible hypothesis accounting for this remarkable stability in thermophilic enzymes states that these enzymes have enhanced conformational rigidity at temperatures below their native, functioning temperature. This study investigates the relationship between thermostability and rigidity using rubredoxin as a case study. The FIRST software is used to calculate local (residue level) and global rigidity for available rubredoxin structures and simulated mutants. Quantitative global rigidity measures indicate that an increase in structural rigidity (equivalently a decrease in flexibility) corresponds to an increase in thermostability. At the level of individual residues, hydrogen deuterium exchange experiments level indicate differential changes in flexibility between mesophilic and thermophilic rubredoxin structures that agree with computational flexibility analysis from the FIRST software.
Michael P Sheetz - One of the best experts on this subject based on the ideXlab platform.
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tropomyosin controls sarcomere like contractions for rigidity sensing and suppressing growth on soft matrices
Nature Cell Biology, 2016Co-Authors: Haguy Wolfenson, Giovanni Meacci, Shuaimin Liu, Matthew R. Stachowiak, Thomas Iskratsch, Saba Ghassemi, James Hone, Pere Rocacusachs, Ben Oshaughnessy, Michael P SheetzAbstract:Cells test the rigidity of the extracellular matrix by applying forces to it through integrin adhesions. Recent measurements show that these forces are applied by local micrometre-scale contractions, but how contraction force is regulated by rigidity is unknown. Here we performed high temporal- and spatial-resolution tracking of contractile forces by plating cells on sub-micrometre elastomeric pillars. We found that actomyosin-based sarcomere-like contractile units (CUs) simultaneously moved opposing pillars in net steps of ∼2.5 nm, independent of rigidity. What correlated with rigidity was the number of steps taken to reach a force level that activated recruitment of α-actinin to the CUs. When we removed actomyosin restriction by depleting tropomyosin 2.1, we observed larger steps and higher forces that resulted in aberrant rigidity sensing and growth of non-transformed cells on soft matrices. Thus, we conclude that tropomyosin 2.1 acts as a suppressor of growth on soft matrices by supporting proper rigidity sensing.
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Tropomyosin controls sarcomere-like contractions for rigidity sensing and suppressing growth on soft matrices
Nature Cell Biology, 2016Co-Authors: Haguy Wolfenson, Giovanni Meacci, Shuaimin Liu, Matthew R. Stachowiak, Thomas Iskratsch, Saba Ghassemi, Pere Roca-cusachs, Ben O’shaughnessy, James Hone, Michael P SheetzAbstract:Cells test the rigidity of the extracellular matrix by applying forces to it through integrin adhesions. Recent measurements show that these forces are applied by local micrometre-scale contractions, but how contraction force is regulated by rigidity is unknown. Here we performed high temporal- and spatial-resolution tracking of contractile forces by plating cells on sub-micrometre elastomeric pillars. We found that actomyosin-based sarcomere-like contractile units (CUs) simultaneously moved opposing pillars in net steps of ∼2.5 nm, independent of rigidity. What correlated with rigidity was the number of steps taken to reach a force level that activated recruitment of α-actinin to the CUs. When we removed actomyosin restriction by depleting tropomyosin 2.1, we observed larger steps and higher forces that resulted in aberrant rigidity sensing and growth of non-transformed cells on soft matrices. Thus, we conclude that tropomyosin 2.1 acts as a suppressor of growth on soft matrices by supporting proper rigidity sensing. Sheetz and colleagues use micropillar arrays to report that the regulation of rigidity sensing involves the tropomyosin-dependent control of the stepwise contractions needed to reach a force level sufficient for integrin adhesion reinforcement.
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fibronectin rigidity response through fyn and p130cas recruitment to the leading edge
Molecular Biology of the Cell, 2006Co-Authors: Ana Kostic, Michael P SheetzAbstract:Cell motility on extracellular matrices critically depends on matrix rigidity, which affects cell adhesion and formation of focal contacts. Receptor-like protein tyrosine phosphatase alpha (RPTPα) and the αvβ3 integrin form a rigidity-responsive complex at the leading edge. Here we show that the rigidity response through increased spreading and growth correlates with leading edge recruitment of Fyn, but not endogenous c-Src. Recruitment of Fyn requires the palmitoylation site near the N-terminus and addition of that site to c-Src enables it to support a rigidity response. In all cases, the rigidity response correlates with the recruitment of the Src family kinase to early adhesions. The stretch-activated substrate of Fyn and c-Src, p130Cas, is also required for a rigidity response and it is phosphorylated at the leading edge in a Fyn-dependent process. A possible mechanism for the fibronectin rigidity response involves force-dependent Fyn phosphorylation of p130Cas with rigidity-dependent displacement. With the greater displacement of Fyn from p130Cas on softer surfaces, there will be less phosphorylation. These studies emphasize the importance of force and nanometer-level movements in cell growth and function.
M. Aguilar - One of the best experts on this subject based on the ideXlab platform.
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Properties of Neon, Magnesium, and Silicon Primary Cosmic Rays Results from the Alpha Magnetic Spectrometer.
Physical review letters, 2020Co-Authors: M. Aguilar, L. Ali Cavasonza, Giovanni Ambrosi, Luísa Arruda, N. Attig, F. Barao, L. Barrin, A. Bartoloni, S. Başeğmez-du Pree, R. BattistonAbstract:We report the observation of new properties of primary cosmic rays, neon (Ne), magnesium (Mg), and silicon (Si), measured in the rigidity range 2.15 GV to 3.0 TV with 1.8 × 10$^{6}$ Ne, 2.2 × 10$^{6}$ Mg, and 1.6 × 10$^{6}$ Si nuclei collected by the Alpha Magnetic Spectrometer experiment on the International Space Station. The Ne and Mg spectra have identical rigidity dependence above 3.65 GV. The three spectra have identical rigidity dependence above 86.5 GV, deviate from a single power law above 200 GV, and harden in an identical way. Unexpectedly, above 86.5 GV the rigidity dependence of primary cosmic rays Ne, Mg, and Si spectra is different from the rigidity dependence of primary cosmic rays He, C, and O. This shows that the Ne, Mg, and Si and He, C, and O are two different classes of primary cosmic rays.
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antiproton flux antiproton to proton flux ratio and properties of elementary particle fluxes in primary cosmic rays measured with the alpha magnetic spectrometer on the international space station
Physical Review Letters, 2016Co-Authors: M. Aguilar, N. Attig, B Alpat, G Ambrosi, L Arruda, P Azzarello, A Bachlechner, Ali L Cavasonza, S Aupetit, F. BaraoAbstract:A precision measurement by AMS of the antiproton flux and the antiproton-to-proton flux ratio in primary cosmic rays in the absolute rigidity range from 1 to 450 GV is presented based on 3.49 × 105 antiproton events and 2.42 × 109 proton events. The fluxes and flux ratios of charged elementary particles in cosmic rays are also presented. In the absolute rigidity range ∼60 to ∼500 GV, the antiproton ¯p, proton p, and positron eþ fluxes are found to have nearly identical rigidity dependence and the electron e− flux exhibits a different rigidity dependence. Below 60 GV, the ( ¯ p=p), ( ¯ p=eþ), and (p=eþ) flux ratios each reaches a maximum. From ∼60 to ∼500 GV, the ( ¯ p=p), ( ¯ p=eþ), and (p=eþ) flux ratios show no rigidity dependence. These are new observations of the properties of elementary particles in the cosmos.
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precision measurement of the helium flux in primary cosmic rays of rigidities 1 9 gv to 3 tv with the alpha magnetic spectrometer on the international space station
Physical Review Letters, 2015Co-Authors: M. Aguilar, N. Attig, B Alpat, D Aisa, A Alvino, G Ambrosi, K Andeen, L Arruda, P Azzarello, A BachlechnerAbstract:Knowledge of the precise rigidity dependence of the helium flux is important in understanding the origin, acceleration, and propagation of cosmic rays. A precise measurement of the helium flux in primary cosmic rays with rigidity (momentum/charge) from 1.9 GV to 3 TV based on 50 million events is presented and compared to the proton flux. The detailed variation with rigidity of the helium flux spectral index is presented for the first time. The spectral index progressively hardens at rigidities larger than 100 GV. The rigidity dependence of the helium flux spectral index is similar to that of the proton spectral index though the magnitudes are different. Remarkably, the spectral index of the proton to helium flux ratio increases with rigidity up to 45 GV and then becomes constant; the flux ratio above 45 GV is well described by a single power law.
Suzanne Laba Cataldi - One of the best experts on this subject based on the ideXlab platform.
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Sexuality Situated: Beauvoir on "Frigidity"
Hypatia, 1999Co-Authors: Suzanne Laba CataldiAbstract:This essay relates scenes from Beauvoir's novels to her views of female eroticism and Frigidity in The Second Sex. Expressions of Frigidity signal unjust power relations in Beauvoir's literature. She constructs Frigidity as a symbolic means of rejecting dominance in heterosexual relations. Thus Frigidity need not be interpreted, as it sometimes is, as a form of bad faith. The essay concludes with some thoughts on the relevance of Beauvoir's view of Frigidity to contemporary feminism.
